I think it is correct, just looking for a second opinion as my level of experience is questionable.

Code java:

/****************************************************************************** * A Statistician keeps track of statistics about a sequence of double numbers. * Outline of Java Source Code for this class was obtained from: * [url]http://www.cs.colorado.edu/~main/edu/colorado/homework/Statistician.java[/url] * * Beth Katz modified it to use different method names and extra methods * January 2007 and January 2008 * The student(s) listed below implemented it. * * @author yourname * ******************************************************************************/ public class Statistician implements Cloneable { /**************************** * class invariant: * - resetting the statistician resets all values here * - these values are computed since the most recent reset * - sumOfValues contains the sum of all values entered (or 0) * - sumOfValues may have a value signifying arithmetic errors * Double.POSITIVE_INFINITY or Double.NEGATIVE_INFINITY * - count contains the number of values (or 0) but may contain * Integer.MAX_VALUE if too many values are entered * - smallestValue contains smallest value entered (or 0) * - largestValue contains largest value entered (or 0) */ private double sumOfValues; private int count; private double smallestValue; private double largestValue; /** * Initialize a new Statistician. * @param none * @postcondition * This Statistician is newly initialized and has not yet been * given any numbers. **/ public Statistician( ) { count = 0; smallestValue = 0; largestValue = 0; sumOfValues = 0; } /** * Reset this Statistician. * @param none * @postcondition * This Statistician is reinitialized as if it has never been * given any numbers. **/ public void reset( ) { count = 0; smallestValue = 0; largestValue = 0; sumOfValues = 0; } /** * Returns a separate copy of this Statistician that will appear * to be indistinguishable from the original but separate * @postcondition * The returned Statistician is a separate copy of this Statistician */ public Statistician clone( ) { Statistician outcome = null; try { outcome= (Statistician) super.clone(); } catch (CloneNotSupportedException e) { e.printStackTrace(); } return outcome; } /** * Give a new number to this Statistician. * @param number * the new number that is being given to this Statistician * @postcondition * The specified number has been given to this Statistician * and it will be included in any subsequent statistics. **/ public void insert(double number) { { if (count == 0) { sumOfValues = number; largestValue = number; smallestValue = number; } else { sumOfValues += number; if (number > largestValue) largestValue = number; if (number < smallestValue) smallestValue = number; } count++; } } /** * Compare this Statistician to another object for equality. * @param obj * an object with which this Statistician will be compared * @return * A return value of true indicates that obj refers to a Statistican * object with the same length, sum, mean, largest and smallest as * this Statistician. Otherwise the return value is false. * Note: * If obj is null or does not refer to a Statistician object, * then the answer is false. **/ public boolean equals(Object obj) { { if( obj instanceof Statistician) { Statistician stat = (Statistician) obj; return (stat.count == count && stat.sumOfValues == sumOfValues && stat.largestValue == largestValue && stat.smallestValue == smallestValue); } return false; } } /** * Determine how many numbers have been given to this Statistician. * @param none * @return * count of how many numbers have been given to this Statistician * since it was initialized or reinitialized. * Note: * Giving a Statistician more than Integer.MAX_VALUE numbers, * will cause failure with an arithmetic overflow. **/ public int length( ) { return count; } /** * Determine the sum of all the numbers that have been given to this * Statistician. * @param none * @return * the sum of all the number that have been given to this * Statistician since it was initialized or reinitialized. * Note: * If the sum exceeds the bounds of double numbers, then the answer * from this method may be Double.POSITIVE_INFINITY or * Double.NEGATIVE_INFINITY. **/ public double sum( ) { if (count == 0){ return 0; } return sumOfValues; } /** * Determine the arithmetic average of all the numbers that have been * given to this Statistician. * @param none * @return * the arithmetic mean of all the number that have been given to this * Statistician since it was initialized or reinitialized. * Note: * If this Statistician has been given more than Integer.MAX_VALUE * numbers, then this method fails because of arithmetic overflow. * If length() is zero, then the answer is Double.NaN. * If sum() exceeds the bounds of double numbers, then the answer * may be Double.POSITIVE_INFINITY or Double.NEGATIVE_INFINITY. **/ public double mean( ) { if(count == 0) { return Double.NaN; } return (sumOfValues / count); } /** * Determine smallest number that has been given to this Statistician. * @param none * @return * the smallest number that has been given to this Statistician * since it was initialized or reinitialized. * Note: * If length() is zero, then the answer is Double.NaN. **/ public double smallest( ) { if (count==0){ return Double.NaN; } return smallestValue; } /** * Determine largest number that has been given to this Statistician. * @param none * @return * the largest number that has been given to this Statistician * since it was initialized or reinitialized. * Note: * If length() is zero, then the answer is Double.NaN. **/ public double largest( ) { if (count==0){ return Double.NaN; } return largestValue; } /** * Add the numbers of another Statistician (addend) to this Statistician. * @param addend * a Statistician whose numbers will be added to this Statistician * @precondition * The parameter, addend, is not null. * @postcondition * The numbers from addend have been added to this Statistician. * After the operation, this Statistician acts as if it were given * all of its numbers and also given all of the numbers from the * addend. * @exception NullPointerException * Indicates that addend is null. **/ public void add(Statistician addend) { if (addend.count != 0) { if (count == 0) { count = addend.count; sumOfValues = addend.sumOfValues; largestValue = addend.largestValue; smallestValue = addend.smallestValue; } else { count += addend.count; sumOfValues += addend.sumOfValues; if (addend.largestValue > largestValue) largestValue = addend.largestValue; if (addend.smallestValue < smallestValue) smallestValue = addend.smallestValue; } } } /** * Create a new Statistician that behaves as if it was given all * the numbers from this and the other Statistician * @param other * an existing Statistician * @precondition * Neither this nor the other Statistician is null. * @return * a new Statistician that acts as if it was given all the * numbers from this Statistician and the other Statistician * @exception NullPointerException. * Indicates that the argument is null. **/ public Statistician union(Statistician other) { if (other ==null && this == null) { throw new NullPointerException(); } Statistician outcome = new Statistician(); outcome.sumOfValues = other.sumOfValues + this.sumOfValues; if (other.largestValue > this.largestValue){ largestValue = other.largestValue; } outcome.largestValue = largestValue; if (other.smallestValue > this.largestValue) smallestValue = other.largestValue; outcome.smallestValue = smallestValue; outcome.count = other.count + this.count; return outcome; } }